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BRAKING SYSTEMS The braking systems used on motorcycles and ATVs, like virtually any type of braking system, reduce the machine’skineticenergyby transforming it into heat energy known as friction heat . Therefore, a brake is an energy-conversion device that converts the energy of motion (kinetic energy) into heat energy. Motorcycle braking is accomplished by the friction (resistance to movement) produced when a brake lining is forced against a rotating drum or disc. Friction between the linings and drum or disc serve to slow and eventually stop wheel rotation. The brakes used on motorcycles fall into two categories: Mechanical drum, sometimes called expanding shoe Hydraulic disc Motorcycle brakes commonly use either hydraulic (fluid pressure) or mechanical (cable or linkage) mechanisms to apply the brakes. Brakes, Wheel Assemblies, and Tires 1 Mechanical Drum Brakes First, let’slookatthedrum brake, sometimes called the mechanical, expanding double-shoe brake ( Figure 1 ). Generally used for rear wheels, this brake is also used on some front wheels. With this kind of brake, a backing plate that’sconnectedtothe forks holds the two brake shoes. The wheel and brake drum rotate around the brake shoes. When the rider applies the brake, a cam pushes the two semicircular shoes outward. The circle formed by the two shoes expands. When the shoes expand, they press against the rotating drum, thereby limiting its free rotation